In my copending U.S. patent application Ser. No. 911,947 filed June 2, 1978, there is disclosed and described an inverter-type power supply for electrical machining which basically comprises a transformerless input means connectable directly to a source of commercial alternating current, a rectifier connected to the input means directly for converting the commercial alternating current to a direct current, a high-frequency transformer having a primary winding connected via a high-frequency switch to the output of the rectifier and a secondary winding connected via a further rectifier to an electrical machining gap and a signal pulser for furnishing signal pulses to the switch. The latter is thus turned on and off at a high frequency with the signal pulses to provide a desired train of machining pulses across the gap. It has been pointed out that this inverter structure provides an improved power supply which is highly suitable for electrical machining and is reduced both in size and weight, is high in stability and efficiency and is practically trouble-free.